Field
The present invention relates to flow control of a cooling medium in a fuel cell system.
Related Art
Conventionally, a technology is proposed by which in a fuel cell system having a cell stack composed of a plurality of stacked unit cells, when the system is started below the ice point, warming up is performed in a state when a cooling water pump is stopped so that the cooling water is not circulated, and the power generation site is heated up rapidly (JP2010-186599A).
However, according to the above-described technology, for a unit cell that is difficult to warm up as compared to other unit cells, such as a unit cell positioned at an end of the cell stack, it is not possible to apply the waste heat via the cooling water from another unit cell. Therefore, distribution of temperature occurs in the cell stack, and a long time is required to warm up the entire cell stack up to a predetermined temperature, which is a problem. Moreover, even within each unit cell, it is not possible to direct the waste heat of the inlet side of an oxidizing gas, which is relatively easy to warm up, toward the outlet side of the oxidizing gas via the cooling water. Therefore, distribution of temperature occurs within each unit cell, and a long time is required to warm up the entire cell stack up to a predetermined temperature, which is a problem. These problems are not restricted to the cooling water, but are a common problem in a fuel cell system in which a cooling medium of any arbitrary type, such as an antifreeze liquid or air, etc., is circulated to adjust the temperature of the cell stack.